The present invention generally relates to information recording and/or reproducing apparatuses, and more particularly to an information recording and/or reproducing apparatus which reproduces a pre-recorded address information from a recording medium when recording and/or reproducing a main information signal on and/or from the recording medium.
Generally, a recording medium such as an optical disc is pre-recorded with an address information for indicating an absolute address on the recording medium. Hence, quick access can be made to a desired address on the recording medium by detecting the pre-recorded address information.
FIG.1 shows a portion of an example of the optical disc. An optical disc 10 comprises a spiral information recording portion 11 and a spiral guide groove portion 12. Each track turn of the information recording portion 11 is provided between two successive track turns of the guide groove portion 12. An address information ADR is pre-recorded on the information recording portion 11 with a predetermined period, and the optical disc 10 is the so-called CLV (Constant Linear Velocity) disc.
FIG.2 shows a portion of the optical disc 10 on an enlarged scale. The address information ADR is pre-recorded on the information recording portion 11 as rows of intermittent pits 13, and the pre-recorded address information ADR is detected by use of a reproducing light beam which forms a light spot 15a on the optical disc 10. The light spot 15a has such a size that the information recording portion 11 and the guide groove portion 12 on both sides thereof are scanned simultaneously so that the tracking of the reproducing light beam can be controlled. The detection of the pre-recorded address information ADR is carried out based on the reflected light from the optical disc 10.
FIG. 3 shows an example of an address detecting system of the conventional information recording and/or reproducing apparatus which reproduces the pre-recorded address information ADR from the optical disc 10 when recording and/or reproducing a main information signal on and/or from the optical disc 10. The address detecting system comprises an optical pickup device 21 which scans the optical disc 10 by use of a reproducing light beam 15 which forms the light spot 15a on the optical disc 10, an information detecting circuit 22, and an address reproducing circuit 23.
When the light spot 15a of the reproducing light beam 15 scans the portion of the optical disc 10 pre-recorded with the address information ADR, the information detecting circuit 22 detects the address information ADR based on a change in the phase or reflectivity of the reflected light from the optical disc 10. The detected address information ADR is supplied to a system controller (not shown) which is a central processing unit or the like through the address reproducing circuit 23 and a terminal 26. The information detecting circuit 22 comprises a detecting circuit 24 for detecting the address information ADR based on an output source signal of the optical pickup device 21, and a binarization circuit 25 for forming a binary signal from an output detection signal of the detecting circuit 24. The information detecting circuit 22 for forming the binary signal is known, and such a circuit is disclosed in a U.S. Pat. No. 4,142,208, for example.
In order to carry out the recording of the main information signal on the optical disc 10 with a high density, a track pitch TP shown in FIG. 2 must be decreased. However, when the track pitch TP is decreased, the address information ADR pre-recorded on the adjacent track turns of the information recording portion 11 will also be reproduced as crosstalk by the light spot 15a when scanning an intended track turn of the information recording portion 11, because the light spot 15a scanning the intended track turn of the information recording portion 11 will also scan at least a part of track turns of the information recording portion 11 adjacent to the intended track turn due to the extremely short separation of two mutually adjacent track turns of the information recording portion 11.
The positions where the address information ADR is pre-recorded are not aligned along certain radial directions on the optical disc 10, since the address information ADR is pre-recorded with the predetermined period. For this reason, when the light spot 15a scans a part of a certain track turn of the information recording portion 11 not pre-recorded with the address information ADR, the address information ADR pre-recorded on a track turn of the information recording portion 11 adjacent to the certain track turn may be reproduced as crosstalk. In other words, during a scanning time of the certain track turn of the information recording portion 11, the address information ADR reproduced as crosstalk from the adjacent track will be detected by the detecting circuit 24 during an interval in which no address information ADR should originally be reproduced from the certain track.
Therefore, the conventional address reproducing system suffers a disadvantage in that the information detecting circuit 22 will also detect as the address information ADR the address information ADR reproduced as crosstalk from the track turn adjacent to the intended track turn of the information recording portion 11. When making access to a certain address on the optical disc 10, the reproducing light beam 15 from the optical pickup device 21 will jump to a track turn in error based on the erroneous address information which is reproduced as crosstalk, and it is impossible to make access to the certain address. There is a possibility that the certain address will be reached by chance even when the erroneous address information reproduced as crosstalk is detected by the information detecting circuit 22, but the access time will most likely be extremely long.